This invention relates generally to improvements in irrigation sprinklers, particularly of the rotating or so-called micro-stream type having a rotatably driven vaned deflector for producing a plurality of relatively small water streams swept over a surrounding terrain area to irrigate adjacent vegetation. More specifically, this invention relates to a rotating stream sprinkler having an improved speed control brake for maintaining the rotational speed of the vaned deflector substantially constant throughout a range of normal operating pressures and flow rates.
Rotating stream sprinklers of the type having a rotatable vaned deflector for producing a plurality of relatively small outwardly projected water streams are well known in the art. In such sprinklers, sometimes referred to as micro-stream sprinklers, one or more jets of water are directed upwardly against the rotatable deflector which has a vaned lower surface defining an array of relatively small flow channels extending upwardly and turning radially outwardly with a spiral component of direction. The water jet or jets impinge upon this underside surface of the deflector to fill these curved channels and to rotatably drive the deflector. At the same time, the water is guided by the curved channels for projection generally radially outwardly from the sprinkler in the form of a plurality of relatively small water streams to irrigate adjacent vegetation. As the deflector is rotatably driven, these water streams are swept over the surrounding terrain area, with a range of throw depending in part on the channel configuration. Such rotating stream sprinklers have been designed for irrigating a surrounding terrain area of predetermined pattern, such as a full circle, half-circle, or quarter-circle pattern. For examples of such rotating stream sprinklers, see U.S. Pat. Nos. 5,288,022; 5,058,806; and 6,244,521.
In rotating stream sprinklers of this general type, it is desirable to control or regulate the rotational speed of the vaned deflector and thereby also regulate the speed at which the water streams are swept over the surrounding terrain area. In this regard, in the absence of speed control or brake means, the vaned deflector can be rotatably driven at an excessive speed up to and exceeding 1,000 rpm, resulting in rapid sprinkler wear and distorted water stream delivery patterns. A relatively slow deflector rotational speed on the order of about 4-20 rpm is desired to achieve extended sprinkler service life while producing uniform and consistent water stream delivery patterns. Toward this end, a variety of fluid brake devices have been developed wherein a rotor element carried by the vaned deflector is rotatably driven within a closed chamber containing a viscous fluid. In such designs, the viscous fluid applies a substantial drag to rotor element rotation which significantly reduces the rotational speed of the vaned deflector during sprinkler operation.
While such fluid brake devices are effective to prevent deflector rotation at excessive speeds, the actual rotational speed of the deflector inherently and significantly varies as a function of changes in water pressure and flow rate through the sprinkler. Unfortunately, these parameters can vary during any given period or cycle of sprinkler operation, resulting in corresponding variations in the water stream delivery patterns for irrigating the surrounding vegetation. In addition, such fluid brake concepts require the use and effective sealed containment of a viscous fluid such as a silicon-based oil or the like, which undesirably increases the overall complexity and cost of the irrigation sprinkler.
There exists, therefore, a need for further improvements in and to rotating stream sprinklers of the type for sweeping a plurality of relatively small water streams over a surrounding terrain area, particularly with respect to maintaining the rotational speed of a vaned deflector at a controlled, relatively slow, and substantially constant rate. The present invention fulfills these needs and provides further related advantages.
In accordance with the invention, a rotating stream sprinkler is provided of the type having a rotatable vaned deflector for sweeping small streams of irrigation water in a radially outward direction to irrigate adjacent vegetation, wherein the sprinkler includes a speed control brake for maintaining a substantially constant deflector rotational speed throughout a range of normal operating pressures and flow rates. A friction plate rotatable with the deflector is urged during sprinkler operation to engage a resilient brake pad retained against a nonrotating brake disk. The brake pad includes tapered contact zones for varying the friction contact radius in response to changes in water pressure and/or flow rate to maintain deflector rotational speed substantially constant.
The rotating stream sprinkler comprises the vaned deflector having an underside surface defined by an array of spiral vanes having generally vertically oriented upstream ends which spiral or curve and merge smoothly with generally radially outwardly extending and relatively straight downstream ends. These spiral vanes cooperatively define a corresponding array of intervening, relatively small flow channels of corresponding configuration. One or more upwardly directed water jets impinges upon the spiral vanes and are subdivided into a plurality of relatively small water streams flowing through said channels. These water streams rotatably drive the deflector and are then projected generally radially outwardly therefrom. As the deflector rotates, these relatively small water streams are swept over a surrounding terrain area.
The friction plate is carried by the deflector preferably at an upper side thereof. Upon water-driven rotation, the deflector and the associated friction plate are pressed axially upwardly to move the friction plate against one side of the brake pad, an opposite side of which is seated against the nonrotating brake disk, resulting in frictional resistance to effectively retard or slow the rotational speed of the friction plate and the deflector. In the preferred form, the brake pad incorporates tapered contact zones at one and preferably both axial sides thereof for increasing the surface contact radius with the friction plate and brake disk in response to increases in water pressure and/or flow rate through the sprinkler. With this construction, the frictional resistance or torque applied by the speed control brake is varied in response to changes in water pressure and/or flow rate to maintain the rotary speed of the vaned deflector substantially constant throughout a range of normal operating pressures and flow rates. In a preferred embodiment, the brake pad is formed from a silicone rubber material, and may be surface-coated with a lubricant such as a thin layer of a selected grease or the like to provide a relatively low coefficient of static friction.
Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.